Summarize Argument
The columnist concludes that the number of species on Earth is probably not decreasing. He supports this by saying that the extinction rate this year will likely be similar to 1970, and that new species are probably emerging at the same rate as in past centuries.
Notable Assumptions
In order for the number of species on Earth not to decrease, the columnist must assume that the extinction rate today and in 1970 is equal to or lower than the rate at which new species are emerging. If extinction is happening faster than new species are emerging, the number of species is decreasing.
A
In 1970 fewer new species emerged than went extinct.
This weakens the columnist’s conclusion by proving his key assumption is false. If fewer new species emerged than went extinct in 1970, the number of species decreased. So, since extinction and speciation rates are likely the same today, the number of species is decreasing.
B
The regions of the world where new species tend to emerge at the highest rate are also where species tend to go extinct at the highest rate.
It doesn’t matter where these species are emerging and going extinct. (B) doesn’t show that the rate of extinction, regardless of where it is happening, is higher than the rate of speciation, so it doesn’t weaken the columnist’s argument.
C
The vast majority of the species that have ever existed are now extinct.
While most species that have ever existed are now extinct, new species are still emerging. (C) doesn't give us any reason to believe that new species aren't replacing those that go extinct, so it doesn’t weaken the conclusion that the overall number of species is not decreasing.
D
There is no more concern now about extinction of species than there was in 1970.
People’s concern about extinction is irrelevant to the columnist’s argument. He is only addressing the actual rates of extinction and speciation, regardless of whether people care about it.
E
Scientists are now better able to identify species facing serious risk of extinction than they were in 1970.
Scientists may be more aware of endangered animals now, but this doesn’t change the fact that "about as many species are likely to go extinct this year as... in 1970." (C) doesn’t address the difference between extinction and speciation rates, so it doesn’t weaken the argument.
Summary
A natural history museum has several displays of wild animals that are made by drying and mounting animal skins. In some of the older displays, the skins have begun to wear out because of low humidity and the heat from the lamps. The older displays use tungsten lamps, but the newer ones use compact fluorescent lamps made for museums. These fluorescent lamps give off the same amount of light as the tungsten lamps but produce less heat.
Strongly Supported Conclusions
The tungsten lamps contribute to the deterioration of the older displays.
Some of the older displays will last longer if the tungsten lamps are replaced by the compact fluorescent lamps.
The animal skins in the newer displays will probably deteriorate more slowly than those in the older displays.
Some of the older displays will last longer if the tungsten lamps are replaced by the compact fluorescent lamps.
The animal skins in the newer displays will probably deteriorate more slowly than those in the older displays.
A
Some of the older displays will last longer if the tungsten lamps that illuminate them are replaced by compact fluorescent lamps.
This is strongly supported. The older displays are deteriorating in part because of the heat of the tungsten lamps. Because the compact fluorescent lamps produce less heat than the tungsten lamps, the older displays would last longer if the tungsten lamps are replaced.
B
The displays that are lit by many compact fluorescent lamps are more prone to deterioration than the displays that are lit by a few tungsten lamps.
This is unsupported. All we know about the compact fluorescent lamps is that they produce less heat than the tungsten lamps and are thus better for the displays. We do not know whether a display lit by many compact fluorescent lamps might be more prone to deterioration.
C
More of the displays are lit by compact fluorescent lamps than are lit by tungsten lamps.
This is unsupported. The stimulus gives us no information about how many displays are lit by each kind of lamp. We know only that “newer displays” are lit by compact fluorescent lamps and “older displays” are lit by tungsten lamps.
D
The newer displays will not be subject to deterioration because of low humidity.
This is unsupported. The stimulus tells us that low humidity contributes to deterioration, but it does not tell us whether the type of lamp affects humidity in any way. We know only that the lamps produce different amounts of heat.
E
The humidity in the museum is lower today than it was when the older displays were first put in place.
This is unsupported. We know that low humidity contributes to deterioration, but we do not know anything about the museum’s humidity levels over time.
Summarize Argument
The economist concludes that consumers often benefit when the government allows a corporation to have a monopoly. She supports this by saying that without competition, the corporation can raise prices and spend less on advertising. The savings can be invested in research or infrastructure, which can then benefit consumers.
Notable Assumptions
The economist assumes that corporations with a monopoly often will use their savings to invest in beneficial research or infrastructure, rather than spending it on things that don’t benefit consumers. She also assumes that other costs of monopolies, like higher prices or fewer options, won't outweigh the benefits of research and infrastructure.
A
The benefits to consumers are typically greater if a corporation invests in expensive research or industrial infrastructure than if that corporation spends the same amount of money in any other way.
This reestablishes the fact that research and infrastructure do benefit consumers, but it fails to address whether companies will actually invest their savings into these things. It also fails to address whether these benefits outweigh the costs of monopolies.
B
The government’s permitting a corporation to obtain a monopoly is advantageous for consumers only if that corporation passes the fruits of at least some of its investments on to consumers.
This shows that monopolies benefit consumers only if the corporation shares the results of its investments. However, it doesn't address whether these benefits outweigh the costs of monopolies or whether companies will actually invest in helpful research and infrastructure.
C
If a corporation obtains a monopoly, the disadvantage to consumers of any higher prices will be outweighed by the advantages from extra investments in expensive research or industrial infrastructure made by that corporation.
This suggests that some monopolies will indeed benefit consumers because the advantages of research and infrastructure will outweigh the cost of higher prices.
D
Even if a corporation is not permitted to obtain a monopoly, it typically invests some money in expensive research or industrial infrastructure.
Irrelevant. The economist's argument is about corporations that are allowed to have a monopoly. The fact that other corporations invest in research or infrastructure doesn't tell us whether monopolies will do the same.
E
If obtaining a monopoly enables a corporation to raise its prices and invest less money in advertising, that corporation will almost inevitably do so.
Even though the corporation will almost certainly raise prices and spend less on advertising, this doesn't tell us if it will then invest the savings into research and infrastructure or if the benefits of those investments will outweigh the costs of monopolies to consumers.
"Surprising" Phenomenon
Why do people who eat lots of sugar tend to have below-average levels of unmetabolized sugar in their blood, even though eating sugar increases the level of unmetabolized sugar in the blood?
Objective
The correct answer should help explain why people who eat lots of sugar have an unexpectedly low level of unmetabolized sugar in their blood. The correct answer might tell us that these people have a feature or engage in an activity that tends to decrease unmetabolized blood sugar.
A
Persons who are overweight tend to have below-average levels of unmetabolized sugar in their blood.
We don’t know whether people who eat lots of sugar are likely to be overweight. In any case, even if they were, we would still expect sugar consumption to increase their unmetabolized blood sugar.
B
Fruits, vegetables, meats, and dairy products often contain as much sugar as sweets.
The specific food source that provides sugar has no clear impact. We have no reason to think eating sugar from fruit or vegetables wouldn’t be expected to increase unmetabolized blood sugar in the blood.
C
Consuming large amounts of sugar causes the body to secrete abnormally high amounts of insulin, a sugar-metabolizing enzyme.
For people who eat lots of sugar, sugar in the blood could be metabolized at an unusually high rate. This could explain why people who eat lots of sugar have below-average unmetabolized sugar levels.
D
Consuming large amounts of sugar can lead eventually to the failure of the body to produce enough insulin, a sugar-metabolizing enzyme.
This makes the discrepancy more difficult to explain. Less of a sugar-metabolizing enzyme would lead to even higher amounts of unmetabolized sugar in the blood.
E
Sugar passes into the bloodstream before it can be metabolized.
Even if the sugar is metabolized after entering the blood, we’re still left wondering why these people have below-average unmetabolized sugar levels in the blood.
Summarize Argument
The astronomer concludes that life on Earth might’ve started with a microbe-carrying meteorite from Mars. While Earth was rendered inhospitable to early life by asteroid strikes, Mars escaped such strikes and therefore could’ve fostered life early in its history. And many meteorites originating on Mars have ended up striking Earth.
Identify Argument Part
The referenced text helps explain how life on Earth could’ve started with a meteorite from Mars. If Mars actually wasn’t able to generate microbial life before Earth was, then there would be no reason to believe the meteorite argument. So, the astronomer makes sure to tell us that Mars could’ve hosted microbial life.
A
It is a claim for which no justification is provided but that is required in order to establish the argument’s main conclusion.
The reference text is justified by the claim that Mars escaped asteroid bombardment early in its history. It’s a reason why Mars might’ve been able to host microbial life even when Earth couldn’t.
B
It is a claim for which no justification is provided and that, if true, ensures the truth of the argument’s main conclusion.
The reference text is justified by the claim that Mars escaped asteroid bombardment early in its history. It certainly doesn’t ensure the truth of the argument’s conclusion, as there could be other factors that limit this meteorite-strike theory.
C
It is a claim for which some justification is provided and that is required in order to establish the argument’s main conclusion.
The claim is certainly justified—Mars wasn’t bombarded by asteroids like Earth was. It’s also required to establish the conclusion. If Mars couldn’t have hosted microbial life before Earth, then the meteorite-strike theory falls apart.
D
It is a claim for which justification is provided and that, if true, establishes the truth of the argument’s main conclusion.
The claim, while justified, doesn’t establish the truth of the argument’s main conclusion. There could be other reasons why the meteorite-strike theory is problematic.
E
It is a claim that provides some support for the argument’s conclusion but that neither ensures the truth of that conclusion nor is required in order to establish that conclusion.
The referenced text supports the conclusion, and is indeed necessary to establish that conclusion. If Mars couldn’t have hosted microbial life before Earth, how could the meteorite-strike theory make any sense?
Summarize Argument
We have a series of conditional statement premises:
Excellent pollination → bees
Beehive → bees
Keeping bees economical → use for homegrown honey
Intermediate conc.:
Gardeners without a use for homegrown honey will tend not to have beehives.
Main conc.:
Gardeners without a use for homegrown honey won’t have excellent pollination.
Identify and Describe Flaw
In the jump from the int. conc. to the main conc., the author assumes that failing to have beehives implies there won’t be excellent pollination. This reverses the statement “beehive → bees.” Beehives ensure bees, but that doesn’t mean beehives are necessary for bees.
Also, in the jump to the int. conc., the author assumes that if keeping bees isn’t economical for someone, they probably won’t have beehives.
A
The argument fails to consider the possibility that obtaining homegrown honey is only one of several advantages of beehives.
The argument doesn’t concern whether it’s a good idea to have beehives. So other benefits of honey are irrelevant.
B
The argument confuses what is necessary for pollination to take place with what would guarantee that it takes place.
The argument doesn’t confuse the statement about pollination. If bees aren’t present, pollination can’t happen. What the argument confuses is whether beehives are necessary for the presence of bees.
C
The argument confuses what is necessary for an abundance of fruits and vegetables with what is usually conducive to it.
The argument doesn’t use the statement about fruits and vegetables as part of how it reaches the conclusion. So there’s no confusion about that statement.
D
The argument fails to consider that bees might be present even in the absence of a particular condition that would ensure their presence.
Although we know beehives ensure bees, that doesn’t mean they’re necessary for bees. So we can’t infer from the lack of beehives that there won’t be excellent pollination. There can still be excellent pollination, because there can still be bees present.
E
The argument bases a claim that there is a causal connection between beehives and excellent pollination on a mere association between them.
There is no causal claim concerning beehives and excellent pollination. The author assumes that lack of beehives implies lack of excellent pollination, but that isn’t a causal claim.
I misspoke at 2:48. Regarding the conditional EBH -> KB, EBH is the subset and KB is the superset. I said it the other way around, making the oldest mistake in the book, sufficiency necessity confusion. Egg on my face.
Summarize Argument
The author concludes that people shouldn’t praise poems for their truth. This view is based on the claim that the excellence of a poem should be based on something that’s rare, not something that’s common. And, truth is something that’s common.
Identify Argument Part
The referenced text is a premise. The author uses the assertion that poetic excellence should be based on something that’s rare to support the view that we shouldn’t praise poems just for expressing truths.
A
It is the overall conclusion drawn by the argument.
The referenced text is not the conclusion. It supports the conclusion.
B
It is a premise that, in conjunction with another premise, is intended to support the argument’s conclusion.
This accurately describes the supporting role played by the referenced text. It’s one of the two premises in the argument.
C
It is a premise offered as the sole support for the argument’s conclusion.
The referenced text is a premise, but it’s not the only premise.
D
It is background information that, in itself, does not provide support for the argument’s conclusion.
The referenced text isn’t just background information. It’s offered to support the conclusion.
E
It is a proposition for which the argument seeks to advance an explanation.
The author doesn’t try to explain why the basis of poetic excellence must be rare.